Liquid filters have been employed in a variety of applications including hydraulic systems, engine lubrication systems, and fuel systems. In these type of systems, a filter cartridge is serviced periodically. This is important to protect equipment from contaminant.
One general type of filtration system is sometimes referenced as “in-tank.” In-tank filter systems are described, for example, in PCT publication WO 2005/063358, published Jul. 14, 2005; and, in PCT publication WO 2008/030323, published Mar. 13, 2008. Each of these two PCT publications is incorporated herein by reference.
In general terms, an “in-tank” filter system, is a system configured to be mounted on a reservoir tank for the liquid involved. The system will typically provide for at least one of: liquid flow to the tank; or, draw of liquid from the tank.
Typically, an in-tank filter assembly includes a housing having a removable, i.e. serviceable, filter cartridge appropriately positioned therein. The service cartridge is periodically removed for servicing, for example when it becomes sufficiently occluded to generate an undesirable level of restriction across the filter media, or when a service interval is passed. Servicing typically involves one of: replacing with a new filter cartridge; replacing with a previously used, but refurbished, filter cartridge; or, in some manner cleaning the removed cartridge and replacing it for further use.
An additional type of liquid filter assembly involves a housing removably secured to a filter head that is not mounted on a reservoir tank. Rather, the housing is mounted on a filter head, filter base or some other form of manifold, which directs liquid to be filtered to the filter system and which provides for removal of filtered liquid from the system. Such assemblies are sometimes referenced as “in-line”, since the filter assembly is typically positioned in one or more liquid flow lines. This type of assembly includes a housing or bowl which is mounted on the filter head, base or manifold, for example through a threaded engagement. A filter cartridge is positioned within the housing or bowl, and engages appropriate portions of the filter head as the housing or bowl is mounted, for sealing interaction to provide for a filtering flow path of unfiltered liquid to the filter cartridge, and filtered liquid from the filter cartridge. In some assemblies, referred to herein as bowl/cartridge assemblies, the filter cartridge (when removable from the bowl) is a service part that is typically removed and is either replaced or refurbished.
Example bowl/cartridge filter assemblies are described in PCT WO 2006/012031, published Feb. 2, 2006, incorporated herein by reference. The particular bowl/cartridge filter assemblies depicted in WO 2006/012031 are provided with certain anti-drain back valve features.
It is important to ensure, during servicing, that the filter cartridge is properly and sealingly positioned within the assembly. Since portions of the housing may block view of the cartridge, during closure of the housing, it is preferable to develop features to help ensure proper alignment and interaction between the cartridge and a remainder of the system, to ensure that the cartridge is properly positioned for use.
In addition, with the continued development of still greater numbers of different applications for liquid filter arrangements and a wide number of various types of systems to use them, it is important to ensure that any filter cartridge that is positioned within the housing of a given filter assembly, is a proper filter cartridge for that assembly.
It is also preferable to provide that any features which are incorporated to ensure proper cartridge positioning, and proper engagement within system, are features that are relatively simple to construct, inexpensive to assemble, and convenient to align in use. Improvements in these areas are sought. In addition, unique alternatives to previously existing systems are desired, in order to ensure that for a given system, there is preferably only one type of cartridge, i.e. an appropriate cartridge, which can be fit into the system for use.